[skara] RFR: pr: update all local branches for commit comments

[Erik Helin]

Hi all,

please review this patch that makes `CommitCommentsWorkItem` properly update all local branches prior to calling `ReadOnlyRepository.commitMetdata`. `ReadOnlyRepository.commitMetadata` is essentially `rev-list —all` for Git and all local refs need to be updated for this to work. In order to make as few networks call as possible I manually merge each local branch with its remote counterpart (instead of doing `pull`).

Testing:
- [x] `make test` passes on Linux x64

Thanks,
Erik

-------------

Commit messages:
 - pr: update all local branches for commit comments

Changes: https://git.openjdk.java.net/skara/pull/1041/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1041&range=00
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/1041.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1041/head:pull/1041

PR: https://git.openjdk.java.net/skara/pull/1041